Various types of clamps are employed to support and direct cables extending between supports and/or structures, such as from a utility pole to a building. One common type of clamp used for such a purpose is conventionally referred to as a drop wire clamp. A drop wire clamp enables a cable or wire, such as a telephone wire or coaxial cable, to be supported and attached to a building, pole, or other support wire in a manner that lessens the potential for compromising the signal transmission capability of the cable or wire. The drop wire clamp also is used because the clamp supports the weight of the cable or wire and maintains tension on the line, while relieving stress on the attachment points of the cable or wire, such as the attachment structure on a pole or building.
Drop wire clamps generally fall into one of two categories: (1) a wire wrap-type drop wire clamp; or (2) a compression-type drop wire clamp. With wire wrap-type drop wire clamps, a wire, such as a portion of a messenger strand, is wrapped around the drop wire clamp to secure the signal carrying cable therein. With compression-type drop wire clamps, the cable or wire is secured to the clamp through pressure exerted on the cable or wire by the clamp. In either type of drop wire clamp, it is important that the clamp does not degrade the quality of the signal carried by the cable or wire by damaging the signal-carrying cable or wire or the insulation of the cable or wire and does not otherwise damage the cable or wire, thereby increasing the likelihood of failure of the cable or wire.
More specifically, a compression-type drop wire clamp secures the cable or wire with a compressive force. Compression-type designs may or may not use a trough to accept the cable or wire, but the distinguishing feature of the compression-type drop wire clamps is that the cable or wire is typically held within the clamp through some type of compressive force or pressure on the cable or wire.
One shortcoming with compression-type drop wire clamp designs is that they may damage the cable through the pressurized contact used to secure the cable or wire to the drop wire clamp. This shortcoming becomes particularly evident when compression-type drop wire clamps are used in conjunction with cables or wires that are relatively fragile or are more apt to suffer damage due to the compressive forces or pressure exerted on the cable or wire by the drop wire clamp. Due to the damage caused by the pressurized contact used to secure the cables, the signal carried by the cable is attenuated, disrupted, or interfered with, making prior art compression-type drop wire clamps unsuitable for use with such fragile cables or wire.
While a variety of different types of cables and wires have been found to be more fragile and more likely to be damaged when used with compression-type drop wire clamps, one type of cable or wire which has generally been found to be unsuitable for use with compression-type drop wire clamps is fiber optic-based cables and wires. This shortcoming of compression-type drop wire clamps has become more pronounced in recent years, as the use of fiber optics in cables and wires has greatly increased, particularly in the communications industry.
Fiber optic cables or wires may be constructed in a variety of ways, but generally include: (1) optical fibers; (2) a loose fitting tube or buffer coating; (3) a protective strength member; and (4) an outer jacket. The optical fiber or optical fibers are generally located at the core of the fiber optic cable. The fiber optic core is surrounded by a loose fitting tube or is covered in with a buffer coating. If a loose fitting tube is used, a plastic buffer tube having an inner diameter greater than the outer diameter of the fiber optic core typically surrounds the core. The plastic tube is sometimes filled with another material, such as silicone gel, to prevent the buildup of moisture between the loose fitting tube and the core. If the buffer coating is used, a thick coating of a plastic-type material is typically applied directly to the outside of the fiber optic core. The use of the buffer coating generally allows the final fiber optic able to be smaller in diameter and more flexible, but the cable is less resistant to external forces. A protective strength member generally surrounds, or is located adjacent to but not surrounding (for example, in the form of Kevlar® strength members which run coextensive with the fiber optic core), the loose fitting tube or the buffer coating. The protective strength member gives strength to the final fiber optic cable and helps the cable resist damage. Finally, the outer jacket is generally made of a PVC material, or some other similar material, and surrounds the other components of the fiber optic cable in order to protect the components from exposure to the elements.
Although the construction of fiber optic cables lessens the potential for damage to the fragile fiber-optic core in general uses, the construction of the fiber optic cables does not protect the fiber optic core from damage from compression-type drop wire clamps. As a result, the use of conventional compression-type drop wire clamps with fiber optic cables damages the cables, typically by crushing or damaging the fiber optic core through the increased compressive force and pressure subjected on the cable by the drop wire clamp. Thus, conventional compression-type drop wire clamps have been found to be ill-suited to use with fiber optic cables. This limitation upon the use of compression-type drop wire clamps has become significant, as fiber optic cables and wires have become more common and often must be connected to supporting structures, such as poles and buildings.